Ink storage containers and inkjet printers

Abstract

The present invention relates to a storage container for ink having a chamber (2) for ink (4) and at least one float (10) vertically movable in the chamber (2), the float floating on the ink (4) and spaced apart from the walls (3) of the chamber (2), and the float almost completely covering the surface (5) of the ink (4) and thus preventing contact with air (7) or gas (7), characterized in that the float (10) is centered between the walls (3) of the chamber (2) by a magnet (12). The invention also relates to an inkjet printer having at least one printing unit comprising a plurality of printheads (32) and at least one storage container (1) according to the invention. The invention advantageously ensures a trouble-free ink supply. The invention is preferably used in industrial inkjet printers.

Description

Technical Field

[0001] This invention relates to a storage container for ink. It also relates to an inkjet printer having such a storage container for ink.

[0002] This invention belongs to the field of graphic industry technology, specifically relating to industrial-grade, high-productivity, and high-quality inkjet printing on flat substrates. This involves spraying micro-droplets of liquid ink in an image-like manner onto a moving sheet, roll, film, or label substrate, preferably paper, cardboard, paperboard, plastic, metal, or composite material, using multiple (or a large number) printheads. In particular, this invention relates to the subfield of liquid ink storage and distribution, specifically the cyclical supply of liquid ink to the printheads, i.e., having ink inflow and ink return. Background Technology

[0003] Industrial inkjet printers with a large number of printheads are typically equipped with what is known as an ink supply system. This system usually includes a main tank. In the forward flow path to the printheads, the system typically also includes at least one line with a pump and a so-called "supply manifold" with a storage container, which distributes ink from the line to each printhead. During the recirculation of ink to the printheads, unused ink is returned to the storage container via a return flow. The return flow may also include a line with a pump and an ink manifold.

[0004] US20100238207A1 has disclosed a storage container of the type described, having a chamber for containing ink and a float that floats on the ink and is spaced apart from the chamber wall and almost completely covers the surface of the ink, thereby preventing it from coming into contact with air or gas.

[0005] DE856066 discloses a float that is centered between chamber walls by a soft centering spring. The use of such a spring is not without reaction force. Furthermore, the spring does not allow the float to make large vertical movements.

[0006] From the perspective of graphic product manufacturers (i.e., printing plants that have prepress, actual printing, and postpress processing), there is always an expectation of trouble-free production. In inkjet printing, this particularly includes trouble-free ink supply, as well as preventing ink from drying out or changing ink properties that could affect printing. Summary of the Invention

[0007] Therefore, one objective of the present invention is to provide an improvement over the prior art, which in particular ensures a trouble-free ink supply.

[0008] This task is solved according to the present invention by means of a storage container having preferred technical features and an inkjet printer having preferred technical features.

[0009] Advantageous and therefore preferred further extensions of the invention can be derived from alternative technical solutions, as well as the specification and drawings.

[0010] The storage container for preferred liquid ink according to the invention, preferably disposed in an inkjet printer, has a chamber for containing ink and at least one float, preferably hollow, that can move vertically within the chamber, the float floating on (and possibly partially in) the ink and spaced apart from the chamber walls, and the float almost completely, i.e., preferably substantially completely, covers the ink surface except for gaps to prevent friction and is thus protected from contact with air or gas, characterized in that the float is centered between the walls of the chamber by magnets, wherein the centering need not be precise, but the gaps on different sides of the float may have slight variations.

[0011] The inkjet printer according to the present invention has at least one printing unit, the printing unit comprising a plurality of printheads and at least one storage container according to one of the above embodiments, characterized in that the storage container is part of an ink supply system for the plurality of printheads, and the storage container is a non-circulating main tank located outside the printer, or a non-circulating intermediate tank located outside the printing unit, or a circulating end tank located in the printing unit.

[0012] Advantageous structure and effects of the present invention.

[0013] This invention advantageously ensures a trouble-free ink supply. It is preferably used in industrial inkjet printers.

[0014] The advantages of this invention are twofold: firstly, it avoids disruptive reaction forces acting on the float; secondly, it allows for significant variations in ink level, and the gap between the float and the wall can be selected to be very small, thus achieving almost complete coverage of the ink surface; and finally, the air or gas above the float can act as a damper for the float, especially at the beginning and end of printing.

[0015] The following describes preferred extensions of the invention (hereinafter referred to as "extensions"). These extensions—provided they are not technically mutually exclusive—can also be combined with each other.

[0016] One feature of this extended scheme is that the horizontal distance between the float and all the walls is substantially equal.

[0017] One extended solution features a float that can be arranged to move vertically relative to the wall with virtually no friction. Contact between the float and the wall can be avoided. The float maintains a distance from the wall via magnetic force, thus preventing friction in this regard.

[0018] One extended solution is characterized by the magnet being disposed non-contactly relative to the ink. The magnet can be disposed within the float or within the wall.

[0019] One extension may be characterized in that a plurality of first magnets on or in the float and a corresponding plurality of second magnets on or in the wall are arranged in terms of their magnetic poles such that a repulsive force acting as a centering force acts between the pairs of the first magnets and the second magnets.

[0020] One extension may feature the provision of a plurality of first magnets on or in the float. It may be specified that at least one first magnet is provided on or in each (horizontal) edge region of the float. Preferably, two or more first magnets may also be provided in the longer edge regions of the float.

[0021] One extension may feature the provision of a plurality of second magnets on or within the walls of the chamber. It may be specified that at least one second magnet is provided on or within each wall of the chamber.

[0022] One extended embodiment features a second magnet that is elongated and arranged with its longitudinal axis perpendicular to the direction of the float. It can be specified that a pair consisting of one first magnet and one second magnet is formed, wherein each first magnet can move parallel to the longitudinal axis of its corresponding second magnet due to the vertical movement of the float. Alternatively, it can be specified that a triplet consisting of two first magnets and one second magnet is formed, wherein the two first magnets can move parallel to the longitudinal axis of their respective second magnets due to the vertical movement of the float.

[0023] One feature of this extended scheme is the existence of multiple horizontally adjacent floats; in other words, the floats can be constructed as multi-part or multi-component structures. It can be specified that these floats are connected to each other. It can also be specified that these floats are not connected to each other.

[0024] One extension may be characterized in that the float also constitutes, in other functions, a measuring device or part of a measuring device for measuring the ink level in the chamber, or in other words, the float also has the function of being a measuring device or part of a measuring device for measuring the ink level in the chamber.

[0025] One extension may be characterized by storing water-based ink in the chamber.

[0026] The features and combinations of features disclosed in the above-mentioned "Technical Field", "Summary of the Invention" and "Extensions" sections, as well as the following "Detailed Description" section—which can be combined with each other in any manner—constitute other advantageous extensions of the present invention. Attached Figure Description

[0027] Figures 1 to 4 Preferred embodiments of the present invention and its extensions are shown. Corresponding features are indicated by the same reference numerals in the figures. For clarity, repeated reference numerals have been omitted in the figures.

[0028] Figure 1 A schematic horizontal cross-sectional view of a storage container according to a preferred embodiment of the present invention is shown.

[0029] Figure 2 Show along Figure 1 A schematic diagram of the vertical cross-section of line II in the diagram.

[0030] Figure 3 Show along Figure 1 A schematic diagram of the vertical cross-section of line III in the diagram.

[0031] Figure 4 A schematic diagram of an inkjet printer according to a preferred embodiment of the present invention is shown. Detailed Implementation

[0032] Figures 1 to 3 The liquid ink storage container 1 for inkjet printing shown includes a chamber 2 with sidewalls 3, in which ink 4 is contained or stored. The chamber 2 may also include a lid (not shown). The stored ink 4 has a horizontal surface 5 and thus an ink level 6 or fill level 6 in the chamber 2, which can be measured by a measuring device 8, particularly a distance sensor 8 (or calculated based on a measured distance 8a to the float 10, see below). Air or gas 7 may be present in the chamber 2 above the ink 4. However, contact between the ink 4 or its surface 5 and the air or gas 7 should be avoided as much as possible. For this purpose, a float 10 is provided in the chamber 2, which floats on the ink 4.

[0033] A gap 11 surrounds the float 10, particularly its edge region 10a, and the wall 3. The float 10 can also be constructed as a multi-part structure, comprising multiple floats (parts) 10b. To center the float 10 within the chamber 2 and between the walls 3, a magnet 12 is provided, whose magnetic force achieves centering. Here, a first magnet 13 is arranged in the float 10, particularly in the edge region 10a, and a second magnet 14 (opposite to the first magnet 13) is arranged in the wall 3. The first magnet 13 and the second magnet 14 can form a pair 15 or a triplet 15a. The magnetic poles 16 of each magnet 12 are arranged accordingly such that the generated magnetic force holds the float 10 substantially centered within the chamber 2 and between the walls 3. That is, either the north pole or the south pole is opposite to each other. The second magnet 14 can be constructed as an elongated shape, as shown, with its respective longitudinal axis 17 oriented in the vertical direction 20. Due to magnetic centering, an annular gap 11 or horizontal distance 21 is formed between the float 10 and the wall 3. The gap 11 or distance 21 reduces or prevents friction between the float 10 and the chamber 2, thereby allowing undisturbed float movement 22 in the vertical direction 20. The first magnet 13 is preferably smaller than the second magnet 14, and in particular, so light in weight that it does not significantly affect the buoyancy of the float 10.

[0034] Figure 4 The image shows an inkjet printer 30 according to the invention for printing on a substrate 30a (as a sheet or roll). The machine includes a printing unit 31 and optional additional printing units 31a, preferably at least four printing units for four-color printing. The printing unit 31 also includes a plurality of printheads 32, which... Figure 4 The ink supply system 33 is also shown. This system includes a main tank 34 located outside the inkjet printer 30, an intermediate tank 35 located inside the inkjet printer 30 and outside the printing unit 31, and a storage container 1, according to the invention, as a terminal tank 36, located inside the printing unit 31. Ink lines 37 guide ink 4 from the main tank 34 via the intermediate tank 35 to the terminal tank 36, and from there circulate it to the printhead 32. The other printing units 31a can be supplied with inks of other colors accordingly.

[0035] List of reference numerals in the attached diagram: 1. Storage container 2 chambers 3. One or more walls 4. Ink 5. Ink Surface 6. Ink level or filler level 7. Air or gas 8. Measuring devices, especially sensors 8a (measured) distance 10 floats 10a Edge region of the float 10b Multiple floats 11. One or more gaps 12 Magnets 13 First Magnet 14 Second Magnet 15. Pair of the first and second magnets 15a A triplet consisting of two first magnets and one second magnet 16 magnetic poles 17. Vertical axis 20 Vertical direction 21. Horizontal distance from the float to the wall 22. Float Motion 30 Inkjet Printers 30a Printing substrate 31 Printing Unit 31a Other printing units 32 printheads 33 Ink Supply System 34 Main Tank 35 Intermediate Tank 36 End Tanks 37. Ink piping.

Claims

1. A storage container for ink, having a chamber (2) for ink (4) and at least one float (10) movable vertically within said chamber (2), the float floating on the ink (4) and spaced apart from the wall (3) of said chamber (2), and the float almost completely covering the surface (5) of the ink (4) and thus preventing contact with air (7) or gas (7), characterized in that, The float (10) is centered between the walls (3) of the chamber (2) by a magnet (12).

2. The storage container according to claim 1, characterized in that, The plurality of first magnets (12, 13) on or in the float (10) and the corresponding plurality of second magnets (12, 14) on or in the wall (3) are arranged in terms of their magnetic poles (16) such that a centering repulsive force acts between the pairs (15) of the first magnets (13) and the second magnets (14).

3. The storage container according to any one of claims 1 or 2, characterized in that, A plurality of first magnets (13) are arranged on or in the float (10).

4. The storage container according to any one of claims 1 to 3, characterized in that, Multiple second magnets (14) are arranged on or in the wall (3) of the chamber.

5. The storage container according to claim 4, characterized in that, The second magnet (14) is elongated and is arranged along the vertical direction (20) with its longitudinal axis (17).

6. The storage container according to any one of claims 4 and 5, characterized in that, A pair (15) is formed consisting of a first magnet (13) and a second magnet (14), wherein each first magnet (13) is able to move parallel to the longitudinal axis (17) of its respective second magnet (14) due to the vertical float motion (22).

7. The storage container according to any one of claims 4 and 5, characterized in that, A ternary group (15a) is formed, consisting of two first magnets (13) and one second magnet (14), wherein the two first magnets (13) are able to move parallel to the longitudinal axis (17) of their respective second magnets (14) due to the vertical float motion (22).

8. The storage container according to any one of the preceding claims, characterized in that, There are multiple horizontally adjacent floats (10b).

9. The storage container according to any one of the preceding claims, characterized in that, The float (10) in other functional respects constitutes a measuring device (8) or part of such a measuring device for the filling level (6) of the ink (4) in the chamber (2).

10. An inkjet printer having at least one printing unit comprising a plurality of printheads (32) and at least one storage container (1) according to any one of the preceding claims, characterized in that, The storage container (1) is part of an ink supply system (33) for the plurality of printheads (32), and the storage container (1) is a non-circulating main tank (34) located outside the inkjet printer (30), a non-circulating intermediate tank (35) located outside the printing unit (32), or a circulating end tank (36) located in the printing unit (32).

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